The present disclosure relates generally to fire protection, and, more particularly, to activation components for fire protection systems, and valves for use in fire protection systems.
Fire sprinkler system installation and operation are subject to nationally recognized codes.
As is aptly pointed out in U.S. Patent Application Publication No. 2013/0199803, dry sprinklers are used in areas that are or may be exposed to freezing conditions, such as in freezers, unheated internal areas, walkways, etc. In typical dry-pipe systems, supply conduits run in a space where the water in the supply conduit is not subject to freezing. A dry sprinkler is attached to such supply conduit and extends into a space where the water would otherwise be subject to freezing.
As Publication No. 2013/0199803 further points out, the typical construction of a dry sprinkler comprises a tube (“drop”) with a pipe connector at the inlet end of the tube (for connecting the inlet end to the supply pipe network of the fire suppression system), a seal member at the inlet end to prevent water from entering the tube, and a mechanism to maintain the seal at the inlet end until the sprinkler is activated. Typically, a nozzle with an outlet and a deflector is attached to the opposite, outlet end of the tube. Also, the tube is sometimes vented to the atmosphere to allow drainage of any condensation that may form in the tube. Such dry sprinklers are disclosed, for example, in U.S. Pat. No. 5,775,431. As shown generally in that patent, the actuating mechanism can include a rod or other similar rigid structure that extends through the tube between the nozzle end and the inlet end to maintain a seal at the inlet end. The actuating mechanism further may include a thermally responsive element that supports the rod or the like at the nozzle end and thereby supports the seal at the inlet end. Alternatively, the tube is also sealed at the nozzle end of the tube, and the rod is supported at the nozzle end by the seal member which is itself supported by the thermally responsive support element. In such arrangements, the space in the tube between the two seal members can be pressurized with a gas, such as dry air or nitrogen, or filled with a liquid such as an antifreeze solution. When an elevated temperature is experienced, the thermally responsive support element fails, thereby allowing the rod to move releasing the inlet end seal (and also any outlet seal at the nozzle end of the tube) to allow water from the supply conduit to flow into and through the tube to the nozzle.
The rigid tube or “drop” portion of such conventional dry sprinklers of the type in U.S. Pat. No. 5,775,431 extends with the nozzle into the unheated area from a wet branch line (located in a heated area) and must be precisely aligned and installed while avoiding various architectural, structural, and mechanical obstructions typically found in commercial or industrial buildings. The installer has to first install wet main and branch supply line piping for a sprinkler system and then measure a suitable length for each dry sprinkler from the branch line to the desired height of the nozzle with respect to a ceiling or the like, as the spacing between the branch and the ceiling or desired position of the nozzle is generally not some accurately predetermined distance. Because the actuation rod has to extend between the inlet seal and the nozzle outlet seal or other support at the outlet end, each dry sprinkler like that in U.S. Pat. No. 5,775,431 is custom made for a given length. An installer will order dry sprinklers for the installation according to the lengths that are measured to within a fraction (i.e. ⅛) of an inch. Delivery typically takes a minimum of seven to ten business days and, depending upon backlog, can take weeks. This delays installation and completion of construction projects. Longer delays occur if mistakes are made in measuring or fabricating the sprinklers or the sprinklers are damaged in transit and replacement sprinklers required, further delaying completion of the installation.
Some manufacturers have addressed installation difficulties at least by providing dry sprinklers with an integral “flexible” drop tube. U.S. Patent Application Publication No. 2013/0199803 discloses such a “dry” sprinkler. Here, a seal 4 at the inlet end of the drop tube 1 is held in place by pressurized fluid between the seal 4 and a seal 12 at the outlet end of the tube at the sprinkler head. While this arrangement provides some flexibility with respect to installation and fabrication by the installer and manufacturer, it leaves the end user with a complicated pressure regulation system to maintain to assure that pressure in the flexible tube is held at an adequate level to prevent water leakage through the inlet end seal from the branch supply line.
A different type of dry sprinkler 12 with a flexible drop 14 is disclosed in U.S. Pat. No. 8,887,822. A flexible link 56 is passed through the center of the integral flexible drop 14 between a pivoting valve member such as a clapper 44 and a plug 24 held in the sprinkler outlet of the nozzle 20 by a fusible element 22. The link 56 is sufficiently flexible so as to conform to bending of the flexible drop 14. Activation of the sprinkler by disintegration of the fusible element 22 at the orifice 22 releases the plug 24 and a spring 66 that pulls on one end of the link to remove an opposing end of the link positioned in something called an “X brace valve latch” 54 holding the clapper 44 closed. This sprinkler can be pressurized with appropriate fluid or opened to atmosphere through vent holes 98. However, what is not explained is what assures that the latch 54 will be cleanly released as it must slide through the elbow without twisting and remove itself from the path of the clapper 44. Also, internal braces 64 have to be provided at any significant bend of the tube 14 or there is a danger that the flexible link 56 will be allowed to go sufficiently slack so as not to be pulled from the latch when the thermally response element triggers.
U. S. Patent Application Publication No. 2013/0319696 discloses another dry sprinkler 100 with an integral flexible drop tube 3 connecting a threaded inlet 1 and an opposing outlet 2. This is an alternative arrangement to assure that a flexible link 10 extending between an inlet valve assembly 13 and an outlet plug 53 does not go slack from bends in the tube, regardless of where the bends in the tube are located. The sprinkler 100 is activated by collapse of the frangible element 56 retaining the plug 53 and spacer 45, permitting the spacer 45 to move and pull the link 10, which mechanically fractures the bulb 11 at the inlet end by twisting a collar 36 on the bulb 11. In the one example given in para. 38, approximately one-half inch of slack can be taken up by the arrangement.
Because of their designs, dry sprinklers must be fabricated to within a fraction of an inch of their installed length, even with flexible tubes. Even the dry sprinkler disclosed in U.S. Patent Application Publication No. 2013/0319696 allows only a larger fraction of an inch leeway than the other, previously identified dry sprinklers. As a result, all must be ordered from and fabricated by a manufacturer, at great expense and time to the installer and end purchaser compared with wet sprinkler system installations.
Although U.S. Patent Application Publication No. 2012/0298383 describes the provision of dry sprinklers with flexible tubes (also known as flexible drops) and weep holes, in practice all or nearly all commercially available, flexible tube equipped dry sprinklers are provided with a relatively long flexible tube having an equally long inner tube that keeps the seal assembly closed. Under pressure, there is deformation in the flexible tube, and there have been issues with leakage if the flexible tube is used by itself without an inner tube.
Another disadvantage of the flexible drop is that it requires a bracket that has to be connected to the ceiling, so there may be limits to the type of ceiling and structure where it can be installed.
It would revolutionize the fire protection industry for installers to be able to fabricate and install on site, a dry sprinkler equivalent to a wet sprinkler system, without employing custom measured and factory built dry sprinkler assemblies.